In the 3rd generation partnership project (3GPP) which is a standardization project of a mobile communication system, a technology for selecting, from a plurality of cells operated at different frequencies, a target cell to be used as a serving cell has been proposed.
Specifically, when start conditions are satisfied, the user terminal measures quality of neighboring cells adjacent to a current serving cell and selects, from cells satisfying selection conditions, the target cell to be used as the serving cell.